Periscopic sextant and other instruments



Jan, 25, 1954 P. F. EVERITT ET AL 2,656,990

I PERISCOPIC SEXTANT AND OTHER INSTRUMENTS Filed Oct. 4, 1949 2 Sheels-Sheet l Jan 26, 1954 P. F. EVERITT ET AL 2,666,990

PERISCOPIC SEXTANT AND OTHER INSTRUMENTS Filed Oct. 4, 1949 2 Sheets-*Sheet 2 FIGA?i /a 46 /7 i fffwfm Patented Jan. 26, Y1954 UNITED STAT PERISCOPIC SEXTAN T AND OTHER INSTRUMENTS hilip Francis Everitt son, Seven Kings, assignments, to British company and George Robert Jamie- England, assignors, by mesne Kelvin & Hughes Limited, a

Application Octoberi, 1949, Serial No. 119,494

Claims priority, application Great Britain (Bctober 5, 1948 (Cl. v33 46) 8 Claims.

This invention relates to periscopic sortants for pressurized aircraft and other instruments (for example su marine sextants or perscopes and aircraft dr..t sights) and its main object is to enable the upper end of the instrument to be pushed out beyond the skin of the aircraft or other vehicle without appreciable inlet or loss of air or water or pressure.

According to the invention a hatch device is mounted on the vehicle and a tube or other guideway which closely receives the periscope tu.; or the like tubular part of the instrument, hatch cover which is normally closed, means for locking the hatch in closed position, means whereby the tubular part can be inserted in the guideway only to an intermediate position when the cover is locked, in which position however the tubular part holds the locking means in unlocked position whereupon the cover can be opened, and t .ye instrument can then be pushed up to its operative position. Preferably also means are provided for locking the periscope tube or the like against downwards remo-val whilst the hatch cover is open. The locking control is preierably effected by means of pawls that enter a groove in the outer surface of the periscope tube.

A constructional form of the invention will new be described by way of exainple with reference to the accompanying diagrammatic drawings wherein:

Figure l is a side elevational view of a hatch and associated periscopic tube (of a sextant) made in accordance with the invention;

Figure 2 is e, vertical sectional view oi the hatch;

Figure 3 is a part sectional view on the line 3 3 on Figure l;

Figure e is a sectional view on the lines 'i--i on Figure 2; and

Figure 5 is a view similar to Figure 4 but showing a modified construction.

The outer periscope tube or sheath iii has a sighting window li at its upper end which is to ISD extend above the skin of the aircraft. Just below this window is an annular recess or groove Si? which has rectangular upper and lower edges. At a lower level the tube has another groove I3 of slightly less dimension axially.

The hatch comprises a housing E5 having a ring li forming an opening through which the periscopic tube can project and which opening can be closed by a hatch cover i3. This cover is carried by a pair of arms i9 the lower ends of which are bifurcated to receive a pivot pin 25 mounted in the housing I6. The arms i9 can This forming part of a toggle the other lever of which is shown at 22. The levers 2l, v22, are pivoted together at 23 and the upper end of lever 22 is pivotally attached at 2t to the two arms i9. The lever 22 is extended to form a projection 28 adapted to ride over a cam 253 which is carried in fixed condition by pin and whereby the toggle is kbroken during most of the hatch closing movement. After this projection rides past `the cam 2S, the toggle can `be straightened thereby vlocking the hatch cover in closed position as shown. The pin 2S is connected by a pair of links 3i to a yoke 32 which is mounted on a spindle 33 rotation or" which in the anti-clockwise direction breaks the toggle and opens the hatch which n10-ves into a space 3i?. This toggle and cam device are more fully den scribed in the specicationof Patent No. 2,57 issued December ll, 1951. The spindle carries an operating lever 3d which has a groove il that contains a sliding rod 35 one end of which protrudes to form a press-button 3i. The inner end of the rod moves a small block 3S (Figure 3) radially of the lever pivot 33 into a concentric slot 3Q in the hatch housing whereby the handle can be then moved to open the hatch cover. The block is connected to the inner member of a Bowden cable le the purpose oi which will be described hereinafter. Normally the block 3B when not in the slot 39 is disposed in the end of the groove 4i in the lever 3ft.

A hatch tube i2 serves as a guide to receive and locate the periscopic tube of a periscopic sextant. The tube :i2 has its upper end formed with a frusto-spherical part i3 which seats in a similarly shaped bearing ring fifi carried by the hatch housing, whereby the tube and sextant can be tilted to a suitable extent. A n @i5 carried by a ring d? enters a vertical slot iii in the tube to prevent rotation of the tube.

The hatch tube carries a casing ES which surrounds the lower end of the tube and contains pawls and other elements particularly seen in Figure 4. The casing 5t contains a pair of pawls 5d the inner ends 52 of which project through openings 53 in the tube and can engage in either of the grooves i2, i3, in the periscopic tube. The other end of the Bowden cable is connected to the middle of a double abutment blocs: 35 slidable around the casing 5t and having two wings engageable by two pivoted pawls 5l, 53 respectively.v The two pawls as shown are pivoted on axes parallel to the tube or guideway t2 and their move vertically in relation to the pin 2u. pin carries a lever 2| tails are directed towards each other to ContactA The pawl 51 is urged by a spring the block 55. |51 whereby it normally has one end 59 engaging the block 55 to prevent it from moving and in this position the other end 65 of the pawl 51 enters through an aperture in the yhatch tube. This end is rounded or chamfered on both upper and lower sides so that it can be pushed back by the periscopic tube when this is inserted into the hatch tube. When the periscopic tube is entered into the hatch tube far enough, the inner nose 60 enters the groove I2 the depth of which is such as to position the pawl 51 so that its end 59 is clear of the block 55 which can then be moved by the Bowden cable upon operation of the press button 31 to permit opening of the hatch cover. The nose 6|? is actually repressed by the first entry of the full diameter of the periscope tube before the groove I2 reaches the nose 65 but in practice the operator pushes the periscope tube up into the hatch tube until the nose |50 snaps into the groove I2. The pawl 58 is urged by the spring 58 whereby it has one end S2 engaged by the other wing of the block 55 which holds the nose 63 on the other end of the pawl out of the annular groove l2 but when the block is moved permits this nose to enter the groove. This nose is rounded on the under side only so that (after the hatch has been opened) it can be pushed aside to permit the periscope tube to be pushed up but not down. Thus when the periscopic tube is entered far enough to bring the groove l into line with the pawls the hatch cover can be opened and the periscope can then be pushed up into eiective position but cannot be pulled down out of the hatch tube. rhe nose S3 is however too wide to enter the groove I3 which is however engaged by the other pawls 54|, 51. The periscopic tube can therefore be pulled down from its operative position after retracting pawls 5d until the noses 55, 53 again enter the groove I2. When the hatch is shut, the nose 63 is retracted and the tube I5 can be removed entirely from the tube A2. When the hatch is closed the tube It can only be inserted in the tube d2 to an intermediate position since the pawl 6i] will prevent further movement. A spring Ill acting under compression returns the parts 55, 48 to their normal (hatch closed) positions. The pawls 5ft engage in the groove I2 before the other pawls engage. When the periscope tube has been moved up to its operative position the pawls 54 engage in the groove I3. The pawl 63 cannot engage in the groove I3 since the latter is too small axially for this purpose.

ln the construction illustrated in Figure 5 the hatch cover operating lever is mounted on a pivotal axis 1|. rhe casing carries a spring pressed locking pin i2 which engages a hole in the lever to prevent it from moving. This hole passes through the lever and contains a control pawl or pin 14 slidable at right angles to the axis, of the tube di?. The inner end of the pin 1G passes through the tube and can enter the groove I2 in the periscope tube, the latter in this construction also having the grooves I2, I3. The lever 10 carries a iinger button |55 which is rotatable about the longitudinal axis of the lever. This button is attached to a rod 8l the end of which adjacent the pin 1t carries a projection (not shown) at right angles to the length of the rod.. The pin 14 is formed with a slot 82. A springj |14 urges the pin 14 towards its normal inner position in which (with the instrument removed) the pin 1li will be projecting slightly more into the hatch tube G2 than is shown. In this inner position the projection on rod SI cannot enter the slot 82. The operator will insert the periscope tube I0 into the hatch tube t2 until the pin snaps into the groove or recess I2 which is the position shown in Figure 5. In this position when the rod is rotated by operation of the button |55 the said projection enters the slot G2 in the pin 1li and moves the pin 14 until its outer end is flush with the outer surface of the lever 10. The inner end of the pin 14 is then clear of the tube 42 and the inner end of the pin 12 is clear of the lever 18. The lever 10 can then be operated to open the hatch cover. A torsion spring 30 urges the rod 8| towards its normal position in which the pin 14 is in the position shown. If the periscope tube is not correctly located the said projection will overlap the end of the slot 32 and therefore cannot enter the slot 82 and the pin 12 prevents movement of the lever. The casing carries a single spring pressed ringer-operable pawl |54 one end of which passes through an opening in the tube and enters the groove in the tube I5. The casing also carries a cam operated pawl 15 which is urged by a spring 19 to engage the groove I2 when the lever 10 is moved to the hatch cover opening position. This pawl is cam shaped below but not at its upper part so that it can be pushed aside to enable the periscope tube to be pushed up to the operative position but by entering groove I2 prevents its being pulled out whilst the hatch cover is open. The pawl is however retracted by means oi a cam-button 15 on the lever 10 when the latter is moved to the hatch-closed position. The lever 1o has a semi-circular shape at 11 with an extension on one end, the semi-circular part surrounding the periscope tube when the hatch is closed to prevent tilting movements. The pawls 14, 15 are in principle the same as pawls 51, 58 respectively of Figure 4. Thus the pawl 15 is too big to enter the groove I3 and the pin 'E4 will not enter the groove I3 as it will be retracted.

We claim:

l. A hatch control device for use with a periscope sextant or other instrument of the kind having a. hatch guideway which closely receives a tubular part of the instrument and a hatch cover on said guideway which is normally closed, comprising cover moving means for moving the hatch cover to open and closed positions, holding means for holding said cover moving means against movement to the cover opening position, and movable means for locking and unlocking the holding means, said movable means projecting into the hatch guideway, and being actuated by the tubular part to the holding means unlocking position whereupon the cover can be opened, and the instrument can then be pushed along the guideway to its operative position.

2. A hatch device as claimed in claim l wherein means are provided for projecting into the path of a part of the tubular part while the hatch cover is open thereby locking the tubular part against downwards removal.

3. A hatch device as claimed in claim l wherein the movable means comprises a pawl a part of which projects into the path of the tubular part and is moved thereby into a position in which the pawl permits opening of the hatch cover.

4. A hatch control device for use with a periscope sextant or other instrument of the kind having a hatch guideway which closely receives a tubular part of the instrument and a hatch cover on said guideway which is normally closed, said tubular part being provided with a recess therein, and comprising cover moving means for moving the hatch cover to open and closed positions, holding means for holding said cover moving means against movement to the cover opening position, and movable means for locking and unlocking the holding means, said movable means projecting into the hatch guideway, and being actuated by the tubular part to the holding means unlocking position whereupon the cover can be opened, and the instrument can then be pushed along the guideway to its operative position, and wherein two pawls are provided one of which constitutes said movable means, and said holding means comprises a movable device which moves with said cover moving means and co-operates with the pawls so that when the pawl constituting said movable rneansv is repressed by the tubular part the cover moving means and the movable. device can be moved to the cover openingr position, and means are provided for moving the other pawl when the movable device moves to its cover opening position to engage said other pawl in said recess in the tubular part to prevent its withdrawal.

5. A hatch control device for use with a periscope sentant or other instrument of the kind having a hatch. gui-deway which closely receives a tubular part oi the instrument and a hatch cover on said guideway which is normally closed, said tubular part having at least one annular recess therein, and comprising cover moving means for moving the hatch cover to open and closed positions, holding means for holding said cover moving means against movement to the cover opening position, and movable means for locking and unlocking the holding means, said movable means having a part thereof projecting into the hatch guideway, and being actuated by the tubular part to the holding means unlocking position whereupon the cover can be opened, and the instrument can then be pushed along the guideway to its operative position, a pawl which engages said recess in the tubular part to prevent withdrawal of the tubular part from the hatch guideway, said pawl being of such shape on one side as to permit insertion of the tubular part into the guideway, said part of said movable means being so shaped on both sides as to permit repression of this part by the movement of the tubular part into and out of the guideway.

6. A hatch control device for use with a periscope sextant or other instrument of the kind having a hatch guideway which closely receives a tubular part of the instrument and a hatch cover on said guideway which is normally closed, said tubular part having iirst and second recesses spaced axially along it, and comprising cover moving means for moving the hatch cover to open and closed positions, holding means for holding.

said cover moving means against movement to the cover opening position, and movable means for locking and unlocking the holding means, said movable means projecting into the hatch guideway, and being actuated by the tubular part to the holding means unlocking position whereupon the cover can be opened, and the instrument can then be pushed along the guideway to its operative position, and wherein rst and second pawls are provided, said rirst pawl constituting part of said movable means, and said holding means comprises a movable device which moves with said cover moving means and co-operates with said pawls so that when said first pawl is repressed by the tubular part the cover moving means and the movable device can be moved to the cover opening position, and means are provided for moving said second pawl when the movable device moves the cover opening position to engage said second pawl in said rst recess in the tubular part to prevent its withdrawal, and wherein said second pawl is larger than said rst pawl so that said second pawl will not enter said second recess in the tubular part which however can be entered by the said rst pawl in the operative position of the instrument.

'7. A hatch control device as claimed in claim 4 wherein the two pawls are pivoted on axes parallel with the guideway and have tails directed towards each other contacting opposite ends of the said holding means.

8. A hatch control device for a periscope sextant or other instrument of the kind having a hatch guideway which closely receives a tubular part of the instrument and a hatch cover on said guideway which is normally closed, and comprising cover moving means for moving the hatch cover to open and closed positions, a part xed relatively to said guideway, a member movable by the operator, a hatch locking pawl which in one position engages the xed part and said moving means to prevent movement of said moving means, a spring urging said pawl to said position, a pin coaxial with said pawl, said pin having one end projecting into said guideway and locatable in a normal position and locatable by said tubular part in a partly repressed position, means whereby the operator can move said pin to a fully repressed position only after it has been moved by said tubular part to its partly repressed position, said pin in its fully `repressed position having its outer end flush with the adjacent surfaces of the xed part and said moving means so as to hold the pawl repressed and permit movement of said moving means for opening the hatch cover.

PHILIP FRANCIS EVERITT. GEORGE ROBERT JAMIESON.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,275,975 Murdock Aug. 13, 1918 1,313,534 Hoffman Aug. 19, 1919 2,554,010 Carbonara May 22, 1951 FOREIGN PATENTS Number Country Date 2,613 Great Britain 1876 

